Introduction

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Applications

Introduction to the Application of Titanium Dioxide in Plastic

The plastic industry is the second largest user of titanium dioxide (takes 25% in the total amount of titanium dioxide), which is the field that has seen the fastest growth with an annual growth rate of 6% in recent years. Among the over 500 titanium dioxide codes, there are over 50 codes that are exclusively for plastic.
As for the application of titanium dioxide in plastic products, besides its high covering power, high lightening power, and other pigment performance, it can also enhance the heat resistance, light resistance and weather resistance of plastic products, protecting plastic products from invasion of UV Rays, improving the mechanical capacity and electrical performance of plastic products.

Since the films of plastic products are much thicker than the coatings of oil paints and printing inks, they do not require high pigment volume concentration, plus it has high covering power and tinting strength, so the average amount used is usually 3% - 5%.
It is used in almost all thermosetting and thermoplastic plastics, such as polyolefins (mainly low-density polyethylene), polystyrene, ABS, polyvinyl chloride, etc. It can mix not only with dry resin powder, but also with liquid containing plasticizer. Another way of application is to process titanium dioxide into color master batch first, and then take it into use.
The particle sizes of most titanium dioxides for plastic are small.
Generally, the particle size of titanium dioxide for coating is 0.2~0.4μm,
while the particle size of titanium dioxide for plastic is 0.15~0.3μm.
In this way, you can get blue grounding, which has a covering effect on most yellowish resin or resin that gets yellowish easily.

General type titanium dioxide for plastic does not usually go through the surface treatment because titanium dioxide coated with inorganic substance such as regular hydrated alumina absorbs the equilibrium water of 1% at a humidity of 60%. At the time of extrusion processing of plastic under high temperature, the water will evaporate, resulting in pores on the surface of plastic. The titanium dioxide not coated with inorganic substance usually requires organic surface treatment (polyhydric alcohols, silane or siloxane).

Since the titanium dioxide for plastic and the titanium dioxide for coating are different, and the former is the titanium dioxide processed and mixed with shear force and treated with organic substance on the surface in low-polarity resin, it can be dispersed better under proper mechanical shear force.

With the constant extension of plastic products application range, many externally used plastic products, such as plastic doors and windows, construction materials and other plastic products used outdoor set high requirements on the weather resistance. Besides required use of rutile titanium dioxide, the surface treatment is also required. Such surface treatment does not usually need the addition of zinc, but only silicon, aluminum, zirconium and etc. Silicon is hydrophilic and dewetting, preventing the appearance of pores on plastic due to water evaporation at extrusion under high temperature, but the amount of surface treating agent shall not be too much generally.

· The composition of plastic includes resin, filling, plasticizer and other auxiliaries (such as colorant, antiager, fire retardant, etc.)

The product processing methods are classified as follows:

The extrusion and blow molding process for plastic films

The extrusion molding process for plastic plates

The injection molding process for plastics

For example: The extrusion and blow molding process for plastic films: resin, filling, axillaries, color master batch ingredients (master batch plus resin) blow molding. For the plastic film, the main equipment used in this process includes double-roll mill, film blowing machine, etc. R-219 /R-2219 are recommended.

The injection molding process includes three stages, i.e. plasticization, injection and molded plastic cooling. The common equipment includes plug-type injector, screw-type injector, and etc.
The quality requirements on the titanium dioxide by plastic products are:

1) Covering Power: The better the covering power of the titanium is, the lighter and thinner the plastic products produced are.

2) Whiteness: It determines the appearance of the light colored or white plastic products;

3) Dispersibility: It impacts the production cost of plastic products. The titanium dioxide not properly dispersed will influence the smoothness and brightness of the products;

4) Weather Resistance: The weather resistance of titanium dioxide must be guaranteed for the plastic products used outdoor and the plastic doors and windows (R-219).

Color Master Batch
Plastic master batch is a color setting material with high concentration and high performance, i.e. the pigment is uniformly distributed with an exceptional concentration in the carrier resin, and forms particles with a certain size. It is mainly made up of core layer (pigment), coupling layer (coupling agent or surface active agent), dispersing layer (lubricant or dispersing agent), mixing toughing layer (carrier resin) and etc.

It is used as a coloring agent in plastic, and is extensively used in the production of film blowing, injection molding, and hot pressing products.

The color master batch has great pigmentation, and can be used easily while saving energy, without causing any dust or sewage. Therefore, it is greatly recognized by users. The color master batch has seen a fast development, plus the production process of color master batch is simple and the investment required is low, therefore, there are hundreds of color master batch factories in China with uneven production scale and technological levels. The small-scale factories generate an annual output of dozens of tons, while the large-scale factories can produce tens of thousands of tons. The competition of products is getting increasingly fierce, and the profit of manufacturing enterprises is on a declining curve. The majority of color master batch is of low quality.

According to incomplete statistics, the titanium dioxide used for production of color master batch is 20,000-30,000 tons every year.

The rutile types used are classified into three grades, i.e. high grade, medium grade and low grade. The high grade is the imported rutile, the medium grade is the domestic rutile, and the low grade rutile is the domestic anatase titanium dioxide.

The color master batch produced with imported titanium dioxide by the largest color master batch manufacturing company, Huizhou Baal Chemical Co., Ltd., is mainly for export. And the color master batch produced with domestic titanium dioxide is mainly to meet the demand from domestic market. However, because of the intense competition, the color master batch produced with anatase titanium dioxide (good whiteness, for indoor use) presents a trend of increase. (R-213 recommended)

The color master batch can be used for color matching of polyvinyl chloride, polyethylene, polypropylene, polystyrene and ABS plastics.

The color master batch is used as an industrial raw material, and its performance advantages and disadvantages are usually indicated in the subsequent products (such as blow molding or injecting molding). Therefore, the performance of titanium dioxide in the color master batch is also mainly indicated in the process of color master batch application.

The color master batch is used as an industrial raw material, and its performance advantages and disadvantages are usually indicated in the subsequent products (such as blow molding or injecting molding). Therefore, the performance of titanium dioxide in the color master batch is also mainly indicated in the process of color master batch application.

It is mainly indicated in the following aspects:

1) Tinting strength of titanium dioxide: It determines the amount of titanium dioxide used for the plastic products with same color (lightening power);

2) Whiteness of titanium dioxide: It determines the appearance of light (white) colored plastic products with same content of titanium dioxide;

3) Dispersibility of titanium dioxide: It impacts the production cost of color master batch and the appearance, luster and other indicators of plastic products;

4) Processability of titanium dioxide: It impacts the production cost of color master batch.